There has been proposed an interactive system that projects an image, which is based on an image signal output from a computer, on a whiteboard or the like with a projector, picks up an image of the projected image with an image pickup apparatus, and recognizes operation of a user applied to the projected image with the computer.
For example, there is known a presentation system including a computer, a projection-type video display apparatus (a projector) that projects a video on a projection surface such as a screen, a selective transmission device that transmits light in a specific wavelength band, an image pickup apparatus that picks up an image of the screen or the like, and a pointing stick (a pointer) that is used for pointing a part of the video, and emits infrared light from the distal end thereof (PTL 1). In such a presentation system (an interactive system), it is possible to superimpose a rendered video rendered by the pointing stick (the pointer) on a basic video.
There is also known an information input system (an interactive system) that includes, in an electronic pen (an information input device), a reflecting unit having a predetermined reflecting pattern, specifies the position of the reflecting unit on the basis of a detection result obtained by detecting a wavelength component in reflected light, and specifies an input position of information by the electronic pen on the basis of the position of the reflecting unit.